has decided to undertake an independent investigation because to date, the signalling system supplier has not identified the cause of the failure.
Forensic analysis by the RAIB
found that the tram involved in the derailment reached the maximum permitted speed of 50mph as it entered the first of three tunnels that stretch for 500 metres.
said that the points were in anunsafe condition through a combination of failures of the three stretcher bars and the lock stretcher bar and their fastenings.
And the RAIB
said Network Rail needed to improve procedures for spotting potential problems.
has now issued four learning points and three recommendations have been made.
issued "urgent safety advice" to First Group, which carries out the day-to-day operation of the trams, and Transport for London, which manages the overall performance of the network.
The second incident in 2012 saw five recommendations by the RAIB
including improvements to the door control circuits and improving the driver's visibility.
has recommended that Network Rail should undertake a fundamental review of the fitness for purpose of the current arrangements and that measures should be taken "to ensure that train drivers are given all the information they need to make movements safely and to address issues on the use of intermediaries when conveying information to drivers.
has said its investigation will include the response to any known defects, the steps taken to repair broken track and will review the technology and systems that are in place to detect potential rail breaks.
published their hard-hitting findings yesterday.
comments came on its website ahead of what was expected to be an interim report today on the derailment of the London to Glasgow Virgin Pendolino train on Friday night.
Staff had placed a notice on the compartment door and attempted to secure it to prevent it being opened, but "this had not been effective", the RAIB